Large dose pen

ABSTRACT

A pen shaped syringe for repetitive injection of individually set doses of a medicine from a cylinder ampoule reservoir comprises a dose setting member which may be rotated to cause a rotative movement of a dosing member and a combined rotative and axial movement of an indicator member indicating the set dose, and a piston drive member which when rotated in one direction moves the piston into the cylinder ampoule. A unidirectional coupling is established between the dosing member and the piston drive member by each member carrying a disc having surfaces with sector shaped saw teeth riding over each other when the dosing member is rotated in the dose setting direction and engaging each other when the dosing member is rotated in the opposite direction corresponding to the direction of rotation by which the piston is moved into the cylinder ampoule. A nut/screw connection is established between a syringe housing and the dose setting member, and means are provided to release the unidirectional coupling between the piston drive member and the dosing member by drawing the coupling discs away from each other.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a 35 USC 371 of PCT/DK92/00267 filed Sep. 7, 1992,the contents of which are incorporated herein by reference.

The invention relates to a pen shaped syringe for repetitive injectionof individually set doses of a medicine from a reservoir in the syringe.

Such pen syringes are especially used by diabetics who have to injectthemselves frequently with an insulin preparation to keep their bloodglucose level within tolerable limits.

With the appearance of insulin preparations having a retarded action andof mixed preparations which make it possible to inject at the same timea preparation meeting an immediate need for insulin and a preparationcovering the basic need for a long time, the time between injections isincreased and so are the doses administered at each injection.

The doses are mainly set by rotating part of the pen syringe relativelyto the rest of the syringe and numbers forming a scale along an edge ofthe one rotatable part of the syringe are moved in relation to anindicating mark on the rest of the syringe to indicate the set dose.Hereby the dose is limited by the fact that only a limited number ofnumbers can be placed along the edge of the rotatable part if they shallbe readable at all. This problem is overcome by imparting the rotatablepart an axial displacement concurrently with its rotation wherebyinstead of a circle a helical line becomes available for dose indicatingnumbers and even a scale covering rotation in excess of one turn.

The pen syringe should be as simple as possible to use, i.e. the normaluse should only imply setting a dose and injecting the set dose, andboth these steps should be simple to perform and this condition is metby most pen syringes. However, not all pen syringes offer theopportunity to cancel a set dose, so if a dose once set is not wantedfor injection the only way to bring the syringe back in its neutralposition is to spill the dose. With syringes by which large doses may beset this is not acceptable.

By a known type of syringe the scale is arranged along a helix havingjust one turn. A helical recess in a cylinder surface of a dose settingmember is engaged by a pin on the syringe housing so that the dosesetting member when rotated is axially displaced along its axis. Afterhaving been axially displaced by the setting of a dose, the dose settingmember is pressed home to inject the dose. The engagement between thepin and the helical recess will cause a rotation of the dose settingmember when it is axially pressed home, this rotation being in theopposite direction of the rotation for setting the dose. The rotation ofthe dose setting member is transferred to a screw/nut mechanism drivinga piston in the syringe forward a distance proportional to the rotation.

The ends of the one turn helical recess are connected by an axialrecess. This enables the setting member to be pressed axially backwithout imparting a rotary movement to this member if the rotaryposition of the member is so that the pin on the syringe housing engagesthe axial recess instead of the helical part of the recess. In this waya set dose may be cancelled by turning the dose setting member furtheruntil the pin engages the axial recess. However, this cancelling featurelimits the effective dose setting rotation of the dose setting member toa little less than one turn, and further, as the demands for precisionof the injected dose set a limit to the size of the dose per turning ofthe screw/nut mechanism, the size of the possible set dose is heavilyrestricted.

Consequently, it is the object of the invention to provide a pen syringeby which large doses may be set, a set dose may be cancelled, and thepossibility of cancellation does not influence the possible size of aset dose or the simplicity of the normal use of the syringe.

This is obtained by a pen shaped syringe for repetitive injection ofindividually set doses of a medicine from a cylinder ampoule reservoir,comprising a dose setting member which may be rotated to cause arotative movement of a dosing member and a combined rotative and axialmovement of an indicator member indicating the set dose, a piston drivemember which when rotated in one direction moves the piston into thecylinder ampoule, a unidirectional coupling between the dosing memberand the piston drive member, the coupling being so directed that a dosesetting rotation of the dosing member is not transferred to the pistondrive whereas a rotation in the opposite direction is, this syringebeing characterized in, that a nut/screw connection is establishedbetween a syringe housing and the dose setting member, and that meansare provided to release the unidirectional coupling between the pistondrive member and the dosing member.

The nut/screw connection provides by mutual engaging threads a morestable guidance of the dose setting member than does a pin engaging arecess. As the cancelling mechanism is not based on an axial recess as areturn path, the dosing rotation of the dose setting member may beperformed for more than one turn, and thereby it is permitted to set alarger dose than the one which can be provided by rotating the pistondrive one turn. The cancelling mechanism is realized as a coupling whichmay disconnect the dosing member from the piston drive, so that the dosesetting member and the dosing member may be rotated back without therotation being transmitted to the piston drive.

The thread of the screw/nut connection of the dosing member and thehousing may have a pitch angle exceeding the friction angle of the nutand screw. Thereby the dosing rotation of the dose setting member may beobtained by simply pressing this member axially back, whereby the screwwill automatically screw itself through the nut and provide a rotativemovement of the dose setting member in the dosing direction. Thisautomatic dosing screw function may more easily be obtained if the outerend of the dosing member is terminated by a knob wherein a press buttonis journaled, the button and the knob having mutually abutting surfacesmade of materials having a friction angle lower than the friction angleof the nut/screw connection.

According to an embodiment of the invention, the dose setting member maycomprise a threaded spindle, the dosing member may be tubular and fitover this spindle, and the spindle may have axial recesses engaged bycorresponding axial beams on the inner side of the bore of the dosingmember. Thereby a dosing member is provided which will follow rotary butnot axial movements of the dose setting member.

The unidirectional coupling between the dosing member and the pistondrive may be provided by coupling parts having circular surfacesprovided with sector shaped teeth having an abrupt and a ramp shapededge, the surfaces by a spring being forced against each other with theramp shaped edge of the teeth on so one surface abutting the ramp shapededge of the teeth on the other surface. When the dose setting member isrotated in the dose setting direction, the teeth on the coupling partswill slide with their ramp shaped parts over each other, whereby thedosing member is axially displaced against the force of the spring andwill jump back each time an abrupt edge of the teeth is reached. Eachjump back may be heard and sensed by the operator, and the pitch of thetoothing may be chosen so that a jump back takes place each time thedose setting is increased by say one unit.

The coupling mechanism may be provided by the syringe having a tubularbasic element, a tubular element surrounding the basic element coaxiallywith it and axially displaceable in relation thereto against the forceof a spring forcing the tubular element to a fixed position on the basicelement, and a lifting fork carried by the tubular element and engagingan outer annual projection on the dosing member to lift the couplingpart thereof out of engagement with the coupling part of the pistondrive when the tubular member is axially displaced on the basic elementagainst the force of the spring away from its fixed position.

In the following the invention will be further described with referencesto the drawings, wherein

FIG. 1 is a sectional side view of a pen shaped syringe according to theinvention,

FIG. 2 is an enlarged view of the part of the syringe in FIG. 1containing the dosing mechanism,

FIG. 3 shows a cross section along the line III--III in FIG. 2,

FIG. 4 shows a side view of the pen syringe in FIG. 1 separated into apart comprising the dosing mechanism, a cartridge holder, and a cap,

FIG. 5 shows the syringe in FIG. 4 put together,

FIG. 6 shows a side view of the syringe with the cap removed and thedosing mechanism part and the cartridge holder drawn away from eachother to allow a cancelling of a set dose, and

FIG. 7 shows schematically the coupling discs of a unidirectionalcoupling.

The pen syringe shown in FIGS. 1-6 is built up around a tubular basicmember 1 having at its one end a part 42 with enlarged diameter, thispart by an annular projection being divided into two, a first part beingprovided with a thread onto which a cartridge holder 2 may be screwedand a second part receiving a tubular member 8. The cartridge holder 2comprises a tubular element designed to accommodate a cartridge andhaving in its side walls axially extending openings through which thecontents of the cartridge may be inspected. Along one of the openings arecessed part 4 of the side wall is provided with a scale showing theavailable amount of medicine, here as the number of international unitsof insulin. At its distal end the cartridge holder 2 is provided withnot seen protrusions protruding inwardly from the cartridge holder wallto hold back the cartridge in the holder and cooperating with an adaptertop 5 on the neck part of the cartridge. This adaptor top 5 protrudesfrom the end of the cartridge holder 2 and is provided with an outerthread onto which a needle hub 6 is screwed to secure the cartridge inthe holder 2. A tubular protective cap 3 may be passed over thecartridge holder 2 when the syringe is not in use.

The tubular member 8 fits with its one end over the second part of theenlarged diameter part 42 of the one end of the basic member 1 and abutswith its edge against the annular projection 7. The other end of thetubular member 8 has a reduced diameter and fits over the basic member 1and is at its outer end surmounted by a part 9 having a further reduceddiameter and carrying an internal thread in engagement with an outerthread on a tubular spindle 10.

A spring 11 abutting at its one end an annular internal projection 12 inthe bore of the basic member 1 and pressing at its other end against abushing 41 transferring the pressure to a set of lifting forks 13, thefunction of which will be described below, and which forks 13 carriedguidingly in openings spaced along the perimeter of the member 8transfer the pressure to the member 8 keeping the edge thereof inabutment with the projection 7 on the basic member 1. Through slots 43in the wall of the tubular basic member 1 the lifting forks 13 projectinto the bore of the basic member and may be displaced axially in theseslots.

The spindle 10 is at its end extending beyond the part 9 secured to adose setting knob 14 and may be rotated by rotating this knob 14. Whenrotated in one direction the spindle 10 and consequently the knob 14 aredisplaced axially away from the tubular member 8.

An indicating sleeve 15 is secured to the knob 14 and forms a skirtdependent from the knob 14 and being accommodated in the space betweenthe member 8 and a tubular housing 16 mounted on the large diameter partof this member 8. A window in the tubular housing 16 is provided with amagnifying glass 17, through which the sleeve 15 may be inspected alonga helical line, when it is rotated and simultaneously axially displacedalong with the knob 14. Numbers indicating a set dose are printed alongthe helical line to show the actual dose through the magnifying glass17.

Rotation of the spindle 10 is transferred to a tubular dosing member 18fitting over the thread of the spindle 10. The transmission isaccomplished by the spindle 10 having one or more axial recesses in itsthread engaged by axial beams 19 on the inner surface of the dosingmember 18. Thereby rotative motion is transferred whereas axial motionis not.

At its end opposite the knob 14 the dosing member 18 forms a part 20 ofa unidirectional coupling through which the member 18 is coupled to apiston drive comprising a coupling part 21 and a drive nut 22 having aninternal thread engaging an external thread on a piston rod 23 which isin its retracted position accommodated in the bore of the tubularspindle 10 and which is made unrotatable relatively to the basic member1 by locking projections 24, which are mounted unrotatably in relationto the basic member 1 and engage axial slots in the thread of the pistonrod 23.

The unidirectional coupling is provided by the dosing member 18 and thepiston drive nut 22 having disc shaped coupling parts 20 and 21,respectively, having at the surfaces facing each other teeth eachforming a part of a sector and each having a ramp shaped and an abruptedge. These discs are shown schematically in FIG. 7. The toothedsurfaces are urged against each other by a spring 25 compressed betweena shoulder 26 at the upper end of the tubular member 8 and an outwardflange 27 at one end of a bushing 28 having at its other end an inwardflange 29 abutting the upper edge of the dosing member. When the dosingmember is rotated in the direction by which the knob is screwedoutwardly, the ramp shaped edges slide along each other displacing thecoupling members away from each other against the force of the spring 25until the abrupt edge is reached and the coupling part is displaced homeby the force of the spring ready to start a new sliding along the rampshaped parts. This overriding prevents the rotation from beingtransmitted to the piston drive nut 22 when the knob is rotated in thedose setting direction but is transmitted when the knob is rotated inthe opposite direction, as the abrupt edges on the coupling parts willthen engage each other. This rotation may be provided by pressing theknob home axially, the thread of the spindle having a pitch allowing itto transform the axial pressure to a rotation. To ease this mechanismthe knob 14 is provided with a press button 30 journaled in the knob 14with a lower surface of the button abutting an upper surface of theknob, the abutting surfaces being made of materials which ensure lowfriction.

The rotation is transmitted to the piston drive part 21 of the couplingand consequently to the piston drive nut 22. When the nut 22 is rotatedby the transmitted rotation it will drive the unrotatable piston rod 23in an axial direction towards the cylinder ampoule 31, and by a pistonfoot 32 the piston rod will press a piston 33 into the cylinder ampoule31.

The piston drive part 21 of the coupling is at its periphery providedwith resilient teeth 34 which collaborate with internal teeth 35 in atubular member 36 rigidly mounted in the basic member 1 to provide adetent allowing rotation of the piston drive nut 22 in an injectingdirection but preventing rotation of the nut 22 in the oppositedirection.

The piston rod 23 is made unrotatable by having an axial recess engagedby locking projections 24 on a piston rod lock member 37. Against theforce of a spring 38 this member is by the upper edge of the cylinderampoule 31 pressed into the end of the basic member 1 in an unrotatableengagement. When cartridge holder 2 containing the cylinder ampoule 31is dismounted by unscrewing it from the basic member 1, the spring 38will press the piston rod lock member 37 free of the basic member 1, andthe piston rod may now be rotated as the lock member 37 may now rotatewith it. Thereby the piston rod may be screwed back through the pistondrive nut 22 to its retracted position. When the cartridge holder with anew ampoule is screwed onto the basic member 1, the lock member 37 ispressed back into its unrotatable engagement with the basic member andthe piston rod is again made unrotatable.

From the functions described it is seen that a dose may be set byrotating the knob 14 in the direction causing a disengaging relativemovement of the coupling parts 20 and 21. The parts 20 and 21 areappropriately toothed in a way making each of the hearable suddendisplacements at the end of the ramps of a pair of teeth sliding alongeach other correspond to e.g. one unit. When the knob 14 is screwedhome, which may be done by pressing the button 30, the rotation istransmitted to the piston drive nut 22 causing a forward movement of thepiston corresponding to the set dose.

If a set dose should be cancelled it is obtained by gripping thecartridge holder 2, which is secured to the basic element 1, and thetubular housing 16, which is secured to the tubular member 8, and bydrawing the cartridge holder 2 and the tubular housing 16 axially awayfrom each other. Thereby the tubular member 8 is axially displaced inrelation to the basic member 1, and the spring 11 maintaining thetubular member 8 in position on the basic member 1 is furthercompressed. By this displacement the lifting forks 13 inserted inopenings in the tubular member 8 are displaced until the lower one oftheir prongs 39 extending inwardly through slots in the basic member 1abuts an annular projection 40 on the dosing member 18. A furtherdisplacement against the force of the spring 11 will displace the dosingmember 18 against the force of the spring 25 and bring the couplingparts 20 and 21 out of their mutual engagement. Now the dosing part canfreely be rotated without the rotation being transmitted to the pistondrive nut, and consequently a set dose may be cancelled by turning thedose setting knob 14 back to its initial position, possibly by pressingit home.

When released the member 8 will by the spring 11 be pressed back intoits original position, and the dosing member 18 will be moved back bythe spring 25 to its nut driving position.

We claim:
 1. An apparatus for use with a pen shaped syringe forrepetitive injection of individually set doses of a medicine from acylinder ampoule reservoir, comprising:a housing, a nut member with aninternal thread fixed in the housing, a dose setting member rotatable ina fist direction to set a dose and in a second direction to inject a setdose, and comprising a spindle with an external thread engaging theinternal thread of said nut member, a dosing member coupled to the dosesetting member to be rotated with this dose setting member, an indicatormember, rigidly connected to the dose setting member to follow axial androtational movement of this dose setting member, a piston drive memberwhich when rotated in said second direction moves a piston into thecylinder ampoule, a unidirectional coupling provided between the dosingmember and the piston drive member, by a first coupling part on thedosing member engaging a second coupling part on the piston drive memberand so directed that the rotation of dosing member induced by dosesetting rotation of the dose setting member is not transmitted to thepiston drive member whereas rotation in the opposite dosing directionis; wherein a nut/screw connection is established between the housingand the dose setting member and means are provided to optionally releasethe unidirectional coupling between the dosing member and the pistondrive member.
 2. An apparatus according to claim 1, wherein the dosesetting member is tubular with a bore fitting over the spindle of thedose setting member, which spindle has axial recesses engaged bycorresponding axial beams on the inner side of the bore of the dosingmember.
 3. An apparatus according to claim 2, wherein the unidirectionalcoupling between the dosing member and the piston drive member isprovided by said first and second coupling parts having circularsurfaces provided with sector shaped teeth having an abrupt and a rampshaped edge, the surfaces being forced against each other by a firstspring with the ramp shaped edges of the teeth on one surface abuttingthe ramp shaped edges of the teeth on the other surface; said firstspring surrounding a part of the dosing member and having a first and asecond end, the first end abutting a shoulder in the housing and thesecond end abutting an outward flange on a first bushing which is fittedon an end of the dose member and further has an inward flange resting onsaid end of the dose member.
 4. An apparatus according to claim 3,wherein the means to optionally release the coupling between the dosingmember and the piston drive member comprises a tubular basic elementhaving a first end with an enlarged diameter carrying a cartridge holderaccommodating an ampoule, and a second end coaxially surrounded by atubular element having a first end with an enlarged diameter fittinginto an end of the housing and fixed to said housing, and a second endwith a reduced diameter forming the nut member, the tubular elementbeing axially displaceable from a fixed position relative to the basicelement against the force of a second spring inside said basic elementand having a first end abutting an internal projection in said basicelement and a second end abutting a second bushing resting on liftingforks which are carried in the wall of the tubular element in openingsperpendicular to the axis; an outer projection on the dosing memberprojects into a space between the arms of the forks so that the forkslift the first coupling part, on the dosing member, out of engagementwith the second coupling part of the piston drive, when the tubularmember is displaced on the basic element.
 5. An apparatus according toclaim 1, wherein the internal thread of the nut member and the externalthread of the spindle of the dose setting member have a pitch allowingtransformation of an axial pressure to a rotation.
 6. An apparatussyringe according to claim 5, wherein an outer end of the dose settingmember is terminated by a knob wherein a press button is journaled, thebutton and the knob having mutually abutting surfaces made of materialsensuring low friction.